A cover structure of an upper unit in which a power source of an outboard motor is provided, the cover structure includes a main body cover including a pair of divided covers connected to each other, the pair of the divided covers being configured to be divided into each other in a left-right direction with respect to a traveling direction of a boat, and an attachable and detachable cover that is attachable to and detachable from a part of an outer surface of at least one of the pair of the divided covers.

A marine propulsion unit includes a motor driving force transmission shaft, a propeller shaft, and a shaft including one of a switching shaft and a drive shaft, and one of the motor driving force transmission shaft and the shaft includes a hollow member, and the other of the motor driving force transmission shaft and the shaft is disposed inside the hollow member.

A cooling structure for an outboard motor comprises an oil case which has an oil chamber for storing lubricant oil for an engine. Said cooling structure further comprises: a main exhaust gas passage which guides exhaust gas to a lower side; a cooling water outbound path which guides cooling supply water taken from outside the outboard motor to an upper side, and cools the periphery of the main exhaust gas passage in the oil case by means of the cooling supply water; a cooling water inbound path which guides cooling discharge water that has cooled the engine to the lower side and cools the oil chamber by means of said cooling discharge water; and a mixed fluid passage which, on a side below the oil case, cools the exhaust gas by mixing the exhaust gas and the cooling discharge water.

An outboard motor includes a bracket, an engine, an upper case, a lower case, a cavitation plate, a transmission, a cooling water passage, a first pump, and a second pump. The transmission includes a drive shaft and a propeller shaft. The cooling water passage is connected to the engine and located in the upper case and the lower case. The first pump is below a lower end of the bracket. The first pump is connected to the transmission and operable to send cooling water to the engine through the cooling water passage. The first pump is a non-positive displacement pump. The second pump is driven by a driving force from the transmission and operable to send the cooling water to the engine through the cooling water passage.

A marine engine assembly for mounting to a watercraft is disclosed. The marine engine assembly has an engine unit, an exhaust system fluidly and a propulsion device. The engine unit includes an engine unit housing, an internal combustion engine and an air intake assembly. The air intake assembly, at least one combustion chamber, and the exhaust system together defining at least in part a gas flow pathway. A sealing valve is provided in the gas flow pathway. The sealing valve has an open position permitting flow of gas therethrough. The sealing valve has a closed position preventing flow of gas therethrough for sealing a portion of the gas flow pathway downstream of the sealing valve from a portion of the gas flow pathway upstream of the sealing valve.

An outboard motor includes an engine, a relay exhaust pipe, a downstream exhaust pipe connected to the relay exhaust pipe, and a propeller to be driven by the engine. The engine includes a plurality of cylinders arranged in series along a vertical direction, a plurality of exhaust ports respectively extending from the combustion chambers of the plurality of cylinders in a sideward direction, and an upstream exhaust pipe connected to the plurality of exhaust ports and extending downwardly. A lower end portion of the upstream exhaust pipe is connected to the relay exhaust pipe from above. The upstream exhaust pipe includes an upstream portion located at a higher location than the lower end portion and extending linearly downwardly. The lower end portion is located closer to the combustion chamber than the upstream portion with respect to a left-right direction.

A marine drive has a primary exhaust outlet on its lower gearcase that discharges a primary flow of exhaust gas from the engine to seawater in which the marine drive is situated. A secondary exhaust outlet is located on the marine drive above the primary exhaust outlet and discharges a secondary flow of exhaust gas from the engine to atmosphere around the marine drive at least when the engine is operated at an idle speed. A tertiary exhaust outlet is located on the marine drive between the primary and secondary exhaust outlets, and discharges a tertiary flow of exhaust gas from the engine to the seawater or to the atmosphere depending upon a current location of the tertiary exhaust outlet with respect to the seawater. A muffler is configured to reduce noise emanating from the tertiary exhaust outlet.

An outboard motor to be attached to a hull of a marine vessel that reduces an amount of oil in blow-by gas reaching a breather chamber includes an internal combustion engine including a cylinder block including at least one cylinder. The cylinder block includes two blow-by gas flow paths to guide blow-by gas from a crank chamber to a breather chamber, and the internal combustion engine is oriented such that a crankshaft extends along a direction perpendicular or substantially perpendicular to a bottom of the hull when the marine vessel is sailing.

An outboard motor includes an engine, a propeller to generate a propulsive force by the drive force of the engine, a lithium ion capacitor, a starter motor to be actuated by a power supply from the lithium ion capacitor to crank the engine, a starter relay provided on a starting power supply line between the lithium ion capacitor and the starter motor, a start switch to be turned on by an engine starting operation by a user to energize a coil of the starter relay from the lithium ion capacitor so as to turn on the starter relay, and a charging controller including a switch to connect the lithium ion capacitor to a charging power source to charge the lithium ion capacitor during the driving of the engine, and to disconnect the lithium ion capacitor from the charging power source when the driving of the engine is stopped.

A V8 engine, each bank of which is configured such that four crank pins connected to four piston pins via a connecting rod are positioned at 90° intervals when viewed from one end of a crankshaft. The four crank pins on the bank side are offset by 60° relative to the four crank pins on the bank side when viewed from the one end.